BMW E61 Hydraulic Liftgate Pump Rebuild

The liftgate hydraulic pump in my 2010 BMW 535xi Touring lost hydraulic fluid level about 2 years following a quick fluid level top off. This time, there were two issues: i) bad seals on the liftgate cylinder; and ii) failure of the seal in the hydraulic pump accumulator piston, leading to leakage below the pump. 

I'll do a writeup on replacement of the lift cylinder separately. This post describes the replacement of seals and o-rings in the pump assembly.

BMW Hydraulic Liftgate Accumulator bore, piston and spring following dissasembly

When your liftgate starts struggling to reach the full open position, troubleshooting is fairly straightforward. The pump is located in the rear compartment, directly below the liftgate cylinder on the left hand side of the car, attached the left rear fender. To access, remove the left hand rear storage compartment door, then remove any audio components hindering access. Be very careful disconnecting the fibre optic connections on the audio components.

BMW Hydraulic Pump - low fluid level, fluid weeping from the accumulator (left side of pump)

Once you can see the pump, you'll note the "+" sign on the side of the plastic fluid reservoir. The oil level should be in the center of the "+" sign. In my case, the fluid reservoir was nearly empty, with traces of hydraulic fluid dripping from the accumulator housing (to the left of the fluid reservoir). 

Unfix the pump, lift to show bottom of accumulator and fluid weeping from vent hole

There are some gymnastics required to unfix the pump. Some can remove the pump without removing the left rear cargo area trim panel. If you're removing the pump for a rebuild, it may be easier to take the time to remove the trim panel. 

Once you have the pump removed from the car, and the hydraulic lines to the cylinder disconnected, you're ready to work on the replacement of seals. In the photo below, working clockwise from 12 o-clock, you have the motor top right. You have the mechanical pump mid right - between the motor and reservoir. The reservoir is bottom right. To the left of the reservoir is a hydraulic accumulator (a piston and spring designed to maintain hydraulic pressure, which holds the liftgate in the open position without the motor / pump running.) Just above the accumulator is a valve body, where the hydraulic lines connect and where the pressure sensor (top left) connects. 

Right side: Motor, pump and reservoir. Left side: Accumulator, valve body, and pressure sensor.

Removing the pressure sensor is straightforward. Remove the two hex head cap screws, and pull the pressure sensor straight up. The pressure sensor is sealed with a single o-ring - 9mm x 2mm. (All o-rings mentioned in this post are described by inside diameter (ID) then thickness. For outside diameter (OD) - double thickness and add to the ID.)

Pressure sensor with cap screws, and o-ring seal at base

I removed the motor, it is sealed to the pump with a single o-ring (41.6 x 2.4mm). I made no attempts to remove any pump components, I removed the pump, tried not to change the indexing of the drive spring, replaced the o-ring and replaced the motor. 

Motor removed. The o-ring stayed in the pump recess, it removed with a pick. 

In order to remove the accumulator piston, you need to split the two halves of the pump assembly. There are two long hex head countersunk screws which hold the two halves together. When you split the two halves, you'll note 5 oil passages which are sealed with small o-rings (4 x 1.5mm). Replacing these o-rings is very simple, just pop out of their recesses and clean any debris with a clean, lint free rag. 

Left and right halves separated - note 5 sealing o-rings.

Once you have the two halves separated, you can disassemble the accumulator. There are four hex head countersunk screws which hold the bottom plate to the accumulator body. Remove them slowly, and remove them equally (a few turns on each screw in rotation) because the bottom plate of the accumulator is under spring pressure. By separating the two halves of the pump, you ensure that the piston is at the top of the bore by removing any hydrostatic pressure remaining under spring tension. 

Accumulator piston removed from bore, note bits of piston seal disintegrating, dirty fluid

The piston will only come out of the bore with the two halves separated. Try to remove the piston square to the bore - to avoid the metal edges of the piston from scoring the aluminum bore. Same when replacing the piston, avoid rocking the piston in the bore, and insert squarely. The piston is a urethane U-cup seal, 35mm ID, 45mm OD, 7mm tall. 

Accumulator disassembled - piston, seal, spring, base and screws

Old accumulator piston seal on the left, new urethane U-cup seal on the right

New seal on the piston, old seal on the right

The final seals which are replaceable are the reservoir to pump seal which is a 39.4 x 3.1mm o-ring, and the reservoir drain/fill port, which is a 6.1 x 1.6mm o-ring. Reassemble in the reverse order of disassembly. Ensure that the accumulator is reassembled before assembling the two pump halves. 

After having rebuilt the pump, and disconnected / reconnected the cylinder hoses, you will need to bleed air out of the system. Reinstall the pump in it's normal location behind the left rear wheel well, but keep the reservoir off the pump. I used some 1/4" vinyl tubing to draw oil from my replacement oil can, and to reject oil and froth from the return line to an empty aluminum can. 

Bleeding the pump using vinyl hose. Note froth returning to the aluminum can. 

I used AeroShell 41 Hydraulic Fluid for this repair

Once the froth turns to a consistent air free oil flow, you can stop bleeding, remove the vinyl hoses, and partially replace the reservoir cup. I then refilled the reservoir using a syringe and vinyl hose to get the fluid level back to the "+" sign on the side of the reservoir. I used a regular stainless steel band clamp to hold the reservoir on the pump. 

Refilling the reservoir with the pump mounted in the car

Reservoir replaced, topped up to the correct level. 

I purchased extra seals when I completed this project, I'll put some seal kits up for sale on eBay for anyone interested in doing this repair.

I've made some repair kits available at this link. 

I've made some hydraulic fluid and refill kits available at this link.

Let me know if you have any questions in the comment section below. 

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BMW N54 E60 E61 x-Drive Oil Pan Leak Repair

If you have an X-Drive AWD BMW, the front differential is mounted to the side of the oil pan, and the right front drive axle runs through a sealed pipe through the oil pan. There are two aluminum covers which retain oil in the oil pan. I originally made a repair to one of these covers 2 years ago when I removed the engine to replace the turbos and do the oil pan and head gaskets. This repair failed almost immediately, and this post will explain why my original repair failed, and what I've done to make sure it doesn't happen again.

Right side of the N54 oil pan, with the right side drive axle and bearing support removed. 

Following my initial repair, the plate started leaking immediately. The engine had been reinstalled in the car, and the bearing support and drive axle already replaced, and the suspension bolted up and torqued. I didn't have the time or appetite to tackle the leak then, so I waited almost 2 years until I had a few other projects to work on to tackle this again. To start with, I removed the right side drive axle (half shaft) and the bearing support. Then, I removed the cover and discovered how little sealant remained between the sealing surfaces. The sealant remaining was brittle and was removed quite easily. I followed the sealant manufacturer's directions (wait 1 hour before applying full torque) but this delay is much too short to avoid squeezing out most of the sealant. This was my critical error.

Previous repair squeezed almost all sealant out of the gap between the sealing surfaces

 Clean up the mating surfaces. I use a plastic bristle brush, a plastic scraper, and scotchbrite pads soaked in brake cleaner to get the surfaces perfectly clean.

Plate cleaned up, old sealant removed, ready for re-sealing

I removed the bearing support and right drive axle without draining the differential fluid. I lost a very small amount of fluid through the axle tunnel, maybe 50ml or so (2 oz). I should top up the diff fluid when I complete the repair. Mating surfaces are clean.

Oil pan mating surface cleaned up, ready for resealing

 The last repair, I used a tube of sealant which I had on hand and was already opened. This time, I planned ahead, and made sure I had a fresh tube of new sealant for this repair.

Permatex Ultra Grey Gasket Maker

 Following manufacturers directions, I applied a 1/4" bead to one surface (the cover), and then assembled the cover with the fasteners, but not applying any torque. Just closing the gap to approximately 1mm, as evenly as possible on all sides.

Apply sealant to one sealing surface (not both)

1/4" 5mm bead of silicone, Circling the fastener holes (recommended in sealant instructions)

I waited 48 hours before applying torque to these cover fasteners - 2 N-m only. This seemed to compress the silicone nicely. I'll fill the oil pan with oil and check for leaks before replacing the drive shaft and bearing carrier - just in case I still have a problem.

Maintain a 1mm gap between sealing surfaces, wait 48 hours before torquing fasteners

The engine oil was refilled, and after another 48 hours, absolutely no sign of oil leaking from the plate. Looks like it will hold. 

Mate surfaces, but do not torque the fasteners. Tighten just until some sealant comes out of the gap

I've also found that I have a minor leak just above this repair - at the bed plate to block interface. A few drops of oil are seeping out around two of the bolt heads. To make this repair - the engine has to be removed from the car, and the bedplate removed (which provides access to the crank and crank bearings). This engine is at 205,000km now (approximately 130,000 miles) and this is a repair that I'd like to put off indefinitely. At least the oil pan to block gasket has held up nicely, no leaks so far. Same for the head gasket and valve cover gasket. 

If you have any questions, don't hesitate to ask in the comments below. 

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Rebuilding BMW Transmission Oil Cooler Hose Quick Connect Fittings

I pulled the BMW E61 into the garage last week to sort out a few issues - rear axle CV boots leaking, oil leak, and low boost pressure. On inspection, I found a leaking transmission oil cooler quick connect fitting, which was spraying oil on the charge air duct from the intercooler to the intake manifold.

The upper (pressure side) tranmission oil cooler quick connect fitting is leaking

I did some research on the internet, could not find any articles about people rebuilding these fittings. This hose costs $170 - expensive to replace for a simple leak. I figured since it was leaking anyway, I would try to take it apart and see if there were replaceable seals. The part numbers of the hoses affected are: 17227570973, 17227571978 and 17227571985.

Once the connection is separated, I took a pick and very easily removed two regular o-rings from the female side of the fitting.

It was easy to remove two standard o-rings from the fitting using a pick. I was careful not to scratch the inside of the connector shell. Once I had the o-rings removed, I noted there were two spacers made from plastic - one green spacer deep in the fitting, and one gray spacer just above the green spacer.

O-rings removed from the fitting, see the green spacer and gray spacer just above. 

The old o-rings were squared off, and not very pliable. They held their out of round shape upon removal. I measured the old o-rings and then estimated what the original uncompressed size would be. They appeared to be standard metric o-rings, and a quick trip to the local o-ring supplier yielded some potential replacements. 

Old o-rings above, new o-rings below. Two per fitting. 

Next step was to stuff the new o-rings into the fitting.  To start with, I used a pick to push the green spacer to the bottom of the fitting, and lift the gray spacer to the top of the fitting. This leaves a groove the width of two o-rings to fit the first replacement o-ring. I stuffed the o-ring into the fitting using some needlenose pliers. 

Start by pushing the green spacer to the bottom of the fitting.

Then - insert the replacement o-ring using needlenose pliers. 

I used the needenose pliers to insert the o-ring into the fitting just above the green spacer, and then to hold one side of the o-ring in the correct position while I used a screwdriver to massage the o-ring into position. With the first o-ring in place between the green and gray spacers, use your pick to push down the gray spacer (and the first o-ring) against the green spacer. 

First o-ring inserted above the green spacer. 

Next step, insert the second o-ring just above the gray ring just as before. With both o-rings inserted, I closed the fittings, cleaned them carefully to remove all traces of oil, so that any new leaks would be apparent. Following a run-up - the two fittings I repaired were both well sealed. I created this simple schematic showing how the o-rings stack in the fitting. 

I've purchased spare O-Rings - if you would like to purchase O-Rings to repair your own fittings, click this link.

If you're careful with the plastic ring and don't break it when disassembling the connection, you may be able to repair it. One other tip - if possible, before disassembling, wash the hoses with soap and water, and get into the release clip side of the fitting with a toothbrush to get as much grit and sand out of the fitting. Blow water out of the release clips using compressed air, and this will make the disconnection a bit easier. Comment below if you have any questions. 

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BMW E61 Turbo Replacement Project - Cleaning Intercooler, Radiator, Power Steering and Transmission Coolers

I made the decision to pull the engine and transmission out of the front of the car when doing the turbo replacement project. I was using quickjacks which give me about 24" of lift - and don't have a 2 or 4 post lift to be able to drop the engine and transmission out of the bottom of the car. One thing that really impressed me about this car was there are 7 heat exchangers / coolers around the front of the car: radiator, AC evaporator, power steering cooler, engine oil cooler, charge air intercooler, transmission fluid cooler and coolant / transmission fluid heat exchanger.

Charge air intercooler - lots of grit came out of the fins.

 It was pretty impressive the quantity of road grit that came out of virtually all the heat exhangers, particularly the intercooler, power steering cooler, and transmission fluid cooler. The AC evaporator, engine oil cooler and radiator protect themselves somewhat because they are stacked behind the transmission fluid cooler. The AC evaporator is quite exposed to grit and debris coming through the kidney grille at speed, blasting the paint and flattenning the fin material.

Halo of grit from flushing the intercooler. 

This car is winter driven daily - and exposed to road salt and grit all winter. The intercooler was about 30% blocked with grit, the power steering cooler about 50% blocked with grit, and the transmission cooler was the worst off - almost 100% blocked with grit.

Transmission cooler - almost completely blocked with road grit.

 Through trial and error - I found that the best method to clean all these aluminum parts was to initally flush with soap and water, and try to get as much grit removed using a high flow / low pressure water hose to avoid damaging the fin material. Once that was done, I used aluminum wheel cleaner - sprayed to soak into the fins as much as possible, and then flushed with water within the prescribed time (a few minutes of application only). This remove a good amount of grit. Then the third stage was to clean out grit using a dental pick set - I needed to do this with the worst heat exhangers only - and since these parts cost between $300 and $700 each - it was worth the time doing a few evenings of dental picking to rehabilitate these parts.

Front end during disassembly - note the sandblasting of the AC evaporator - leaving the kidney grille shape with two lines from a cross brace. 

The transmission cooler is the lowest cooler on the car - and the most packed with grit.

Transmission cooler - almost completely blocked with grit.

During the dental picking, I also straightened and lifted any folded fin material - it's time consuming, but for me it was worth it.

Radiator after cleaning with aluminum wheel cleaner. 

AC evaporator after cleaning with aluminum wheel cleaner. 

Intercooler during cleaning - all the metal and fins were in good condition without any pitting at the hose mating surfaces.

One final thing to note - I replaced all the o-rings / sealing rings at all the hose interfaces to help ensure I wouldn't have any leaks at startup. Now that the car is on the road, running, and AC system charged - I can state that it was worth the effort - no leaks at all from any of the systems - cooling, power steering, transmission cooling, engine oil cooling. All good.

Front end with all the coolers replaced. Shop dog hanging out the garage. Not easy keeping the dog clean....

I'll post some additional articles with lessons learned from this project, hopefully it can help others out when doing similar work.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts.

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BMW E61 Turbo Replacement - Engine Subframe Powdercoating, Steering Rack Rebuild

In order to pull the engine out of the front of the car with the transmission, the subframe needs to be dropped in order to allow the oil pan to pass over the steering rack. With the subframe on the floor, it was pretty easy to clean it up and check the condition of the subframe and steering rack.

Here's the subframe. Carbon steel construction, with one engine mount, 2 heat shields and steering rack attached.

The engine subframe on the BMW E61 is fabricated from carbon steel, painted or powdercoated black in the factory. My car is 9 years from the date of manufacture, and has been operated in Toronto and Montreal its entire life, subject to Canadian winters and road salt. What's interesting is that there is virtually no rust anywhere on the steel and aluminum body components. Most of the underbody structural and suspension components are made from aluminum - like the rear suspension frame, and the front suspension arms. There are a few components which sufferred from corrosion - the subframe, some of the aluminum heat shields, particularly at attachment points to the body, and one driveshaft tunnel brace also made of steel which I decided to replace.

The subframe was the one component of the car showing the most significant rust damage

Once I had a look of the extent of the paint bubbling and corrosion on the subframe, I decided that I didn't want to invest the time to try to clean it up and treat the corrosion myself - I had lots of other things requiring attention, like getting the new turbos, head gasket, oil pan gasket, etc on the engine and get the engine / transmission ready to replace in the car. So I decided to strip the subframe, remove the steering rack, and take the subframe to a local powdercoating shop to have it sandblasted and coated.

In preparation for sending out the steering rack - I measured the tie rod locations precisely for setup on reinstallation.

I found a local powdercoating shop that normally does industrial work, and the owner was a bit of a car guy and accepted to do my subframe for $150 - which was a great deal in terms of how much time it saved me from cleaning this up myself.

Subframe back from Powdercoat - beautiful.

He did a great job of sandblasting out all the rust, you can see in the powdercoat finish some of the pitting in the steel which was now overcoated, this should help keep the car on the road for another 10 years. He also protected all the studs and weldnuts from powdercoat - I didn't have any threading or tapping to do - which also saved time.

You can see some of the rust pitting in this photo - right hand motor mount area.

And some of the pitting here.

For the steering rack and axle half shafts / CV joints - I took them all to Axle Automotive (Capital Dominion Radiator) on Gladstone Avenue in Ottawa for rebuild. The rear axle half shafts were both spraying grease, and the fronts were fine but I had them repacked with new boots as a preventative measure anyway. They stripped down the steering gear, cleaned it, replaced the rod seals and boots, and the steering gear seals. I had the option of having the rack painted black - I opted to keep it natural aluminum. It turned out really nice - and now with the car on the road I can report that the steering feel is excellent - rack is performing like new. The price for the rebuild was very good - better than I could find at any shop in the Montreal area.

Front axle half shafts and steering rack - back from rebuild with all new boots. 

The aluminum body of the steering gear shows some oxidation - purely cosmetic and something I can live with. 

One thing to note is that all the bolts holding the subframe to the car front frame are torque to yield type fasteners that need to be replaced when loosened or removed. I did purchase new fasteners for the subframe.

Subframe prepped with heat shields, steering rack, left hand motor mount and power steering lines ready for the motor.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts. Capital Radiator in Ottawa did the steering rack rebuild.

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